1. Field of the Invention
The present invention relates to a semiconductor light emitting device having an intermediate layer between a p-type cladding layer and a contact layer.
2. Description of the Related Art
In the past, as a semiconductor light emitting device such as a light emitting diode (LED) that emits light in green to red waveband, AlGaInP semiconductor light emitting devices have been known. Such an AlGaInP semiconductor light emitting device includes, for example, an n-type cladding layer, an active layer, a p-type cladding layer, and a contact layer in this order over a GaAs substrate.
However, in the AlGaInP semiconductor light emitting device, for example, voltage drop is large in a hetero junction between the p-type cladding layer containing AlGaInP and a contact layer containing GaP, and accordingly a voltage for driving the device (driving voltage) is easily increased. Further, lattice defect and a crosshatch structure are easily generated due to lattice mismatching in such a junction. In result, the driving voltage is increased, the device is easily deteriorated, leading to lowered reliability.
Thus, in the AlGaInP semiconductor light emitting device, a technology for providing an intermediate layer containing AlGaInP or GaInP between the p-type cladding layer and the contact layer to resolve the foregoing disadvantages has been known (for example, Japanese Unexamined Patent Application Publication No. 2001-267631). Specifically, the intermediate layer composed of p-type AlGaInP or GaInP is provided so that the lattice matching ratio Δa/a to the GaAs substrate becomes, for example, −2.5%.